A compound comprising 1-methyl-3-(2′,2′,2′-trifluoroethyl)imidazolium cation and —N(SO2CF3)2 imide anion is known to have fluoroalkyl and imide anion. This compound is useful as hydrophobic, highly conductive ambient-temperature molten salts (Inorganic Chemistry, vol. 35, pp. 1168-1178 (1996)).
A method for producing such 1-methyl-3-(fluoroalkyl)imidazolium imide is known. In this method, fluoroalcohol is allowed to react with trifluoromethanesulfonic anhydride, the reaction product is then allowed to react with 1-methylimidazole to obtain 1-methyl-3-(fluoroalkyl)imidazolium trifluoromethanesulfonate, and the resultant is allowed to react with lithium imide salt to obtain 1-methyl-3-(fluoroalkyl)imidazolium imide by salt exchange (Inorganic Chemistry, vol. 35, pp. 1168-1178 (1996)). This conventional method, however, was seriously deficient from the viewpoints of yield, which was as low as 15% as the total yield from 1-methylimidazole, and difficulty in obtaining a highly purified product.
It was reported that (2,2,2-trifluoroethyl)(phenyl)iodonium bis(trifluoromethanesulfonyl)imide had been synthesized and this could be used as an agent for introducing trifluoroethyl (Chemical Communication, 1998, pp. 2241-2242). However, (2,2,2-trifluoroethyl)(phenyl)iodonium bis(trifluoromethanesulfonyl)imide had low crystallinity, and thus, isolation or purification thereof was disadvantageously complicated.
In the production of (2,2,2-trifluoroethyl)(phenyl)iodonium bis(trifluoromethanesulfonyl)imide, there was only one known suitable reaction solvent, i.e., 1,1,2-trichlorotrifluoroethane (CFC-113) (Chemical Communication, 1998, pp. 2241-2242). CFC-113, however, was an ozone depleting substance and had caused severe environmental destruction. Thus, industrialization thereof was difficult.
Although fluoroalkylaryliodonium sulfonate is known (Bulletin of the Chemical Society of Japan, vol. 60, pp. 3307-3313 (1987) and U.S. Pat. No. 4,873,027 (JP Patent Publication (Kokoku) No. 3-58332 B (1991)), fluoroalkyl and imide anion cannot be simultaneously introduced with the use of this compound.
As described above, there was no method that could simultaneously and efficiently introduce fluoroalkyl and imide anion.
Recently, triazolium imide salt having Rf′CH2CH2— (wherein Rf1 is C1-6 perfluoroalkyl) has been reported as an ambient-temperature molten salt (Journal of Organic Chemistry, Vol. 67. pp. 9340-9345(2002)). However, triazole compound as a starting material is expensive and it requires at least three reaction steps.
Further, ammonium imide salt having Rf″CH2CH2— (wherein Rf″ is C4-10 perfluoroalkyl) has been reported (Tetrahedron Letters, Vol. 44. pp. 9367-9370(2003)). However, it requires two reaction steps to synthesize the ammonium imide salt having Rf″CH2CH2—.